Light-emitting device (hereinafter referred to as “LED” as appropriate) that emit white light by using an excitation light source emitting light in a near ultraviolet or short wavelength visible range in combination with a phosphor came into common use and have recently found practical application to image display devices and illumination devices. In particular, phosphors that emit red fluorescence (hereinafter referred to as “red phosphors” as appropriate) are used for light-emitting devices for image display devices and illumination devices, and light emission properties thereof have been improved variously. Of these, the development of a phosphor having a narrow full width at half maximum in a specific wavelength band is regarded as important in order to achieve both efficiency and color rendering property.
In order to realize both high efficiency and color rendering property of an image display device and an illumination device, for example, a red phosphor having an emission peak wavelength of an emission spectrum of 590 nm or more and 650 nm or less and a full width at half maximum of the emission spectrum of 1 nm or more and 80 nm or less can be effectively used. For this reason, the development of red phosphors having the above-mentioned emission properties has been carried out.
Non-patent document 1 discloses a Mn4+-activated oxyfluoride phosphor such as Mg28Ge7.5O38F10:Mn4+ as such a phosphor. Further, for example, Patent document 1 discloses a Mn4+-activated fluoride phosphor such as a fluorogermanate phosphor.